Electric switch



Oct. 24, 1944. L, T. RAbER 2,361,238-

ELECTRIC SWITCH Filed June 26, 1943 gg- 1 ull I 'lllllllllllllllPERMANENT 71 MA GNET Inventor: I Louis T Render '3 btor'nq Patented Oct.24, 1944 ELECTRIC SWITCH Louis T. Rader, Schenectady, N. Y., assignor toGeneral Electric Company, a corporation oi New York Application June 26,1943, Serial No. 492,431

4 Claims.

My invention relates to electric switches, more particularly tomechanically operated limit switches, and has for its object a simpleand reliable magnet snap action mechanism for snapping the movableelement of the switch between its two positions.

My invention is especially useful in limit switches of the typedescribed and claimed in Patent 2,175,932, issued on October 10,1935, toKenneth J. Unwin. The device of this patent is provided with a permanentmagnet for effecting a snap action of the movable switch element, thismagnet having two pairs of pole faces engaged alternately bymechanically operated armatures. One of the pole faces of each pair isspaced slightly from the armature when in its attracted position toprovide an air gap. While this arrangement is perfectly operable, it hasbeen found that in installations requiring operation of the switch manymillion times, the striking of each armature on the single pole facegradually pounds down the pole face which reduces the length of the airgap between the armature and the other pole face of the same pair, andconsequently increases the magnetic holding force applied to thearmature. This increased holding force causes increased Wear on variousparts of the mechanism with the result that the mechanism wears outquickly.

In accordance with one form of my invention,

I provide as before a single pole for engagement with each of the twoarmatures, but in placeof an air gap between two other poles of themagnet and the armatures respectively, I extend or position the magnetso that the air gap is formed with relation to the hub of the switchoperating member bearing the armatures. Thus the air gap is independentof the position of the armature and the pole faces of the magnet may behammered down by the impact of the armatures for an indefinite timewithout affecting the length of the air gap.

, For a more complete understanding of my invention, reference should behad to the accompanying drawing in which Fig. 1 is a plan view of alimit switch embodying my invention; Fig. 2 is a side elevation view ofthe device shown in Fig. 1; and Fig. 3 is a view partly in section takenalong the line 33 of Fig. 1 looking in the direction of the arrows.

Referring to the drawing, in one form of my invention I provide a switchoperating shaft which is square for convenience in attaching the variousswitch parts to it, except at its ends which are cylindrical androtatably supported on the upright supports II and I2 secured to ametallic base member [3. The operating shaft in is provided with ahelical snap spring l4 surrounding a cylindrical hub Ma attached to theshaft and having its ends on opposite sides of two pins l5 and 3extending lengthwise of the shaft. an armature member ll, rigidlymounted at its lower end on the shaft, and a laterally extendingprojection 18 which is movable through a-predetermined angle betweenprojections l9 and 20 carried by the armature member H. The projectionI8 is mounted in a hollow cylindrical member 20a which forms a bearingfor the righthand end of the shaft l0 and is in turn jour nalled in thesupport I2. In order to give an initial restraining force to effect thesnap action, a permanent magnet 2| is mounted in position with itscenter line passing through the axis of the shaft l0 and perpendicularthereto to restrain the armature member for movement in each direction.The magnet also holds the armature member in each position to which thearmature is snapped.

In accordance with my invention, I provide a single pole piece 22 at thelower end of the magnet, which pole-piece extends transversely withrespect to the center line of the magnet.2l and is in a predeterminedspaced relation with an arcuate section 23 on the armature member. Thusmagnetic flux passes from the pole piece 22 through the air gap 22a tothe armature member, and thence through one or the other of the two armsHa and Nb of the armature member and one or the other of the pole pieces24 or 25 to an upper pole piece 26 on the magnet 2|. It will be notedthat each of the two arms together with the arcuate section constitutesan armature.

The permanent magnet 2| preferably is made of a material having a highcoercive force and,

a high resistance to change in magnetic properties due to shock. Onesuch material is an alloy of 12 per cent aluminum, 25 per cent nickel,and 5 per cent copper, the balance being mainly iron, such as describedand claimed in Patent 1,947,274, issued on February 13, 1934, to WilliamE. Ruder, and Patent 2,027,997, issued on January 14, 1936, toTokushichi Mishima.

The upper magnet pole piece 26 is provided with two pole faces 26a and261) at its opposite ends which are bevelled downward and preferablylie'in planes passing throughthe axis of the shaft [0. The armature polepieces 24 and 25 have pole faces which likewise lie in planes These pinsare secured, respectively, to

piece 22 and the armatures, such as the air gap 21 between the side ofthe pole piece 22 and the left-hand arm of the armature member, is manytime greater than the air gap 22a betweenthe end of the pole piece 22and the portion 23. This air gap 27, furthermore, can be increased ifdesired and made much greater than shown on the drawing. In any case, itis long enough so that a great amount of pounding down of the faces 26aand 282) can be effected without any effect on the length and functionofthe air gap between the parts 22 and 23. Of course, it will beunderstood that when the armature member is thrown to itscounterclockwise position with the pole piece 25 in engagement with thearmature face 261), an air gap similar to the air gap 21 is providedbetween the right-hand arm of the armature member and the pole piece 22.Preferably, the movable pole pieces 24 and 25 are hardened to reduce thewear and hammering effect on them.

In the operation of this switch the operating shaft I is operatedbymechanical engagement of a part carried by the member 200. with anoperating member secured to the moving part of the machine beingcontrolled, such as paper planer, milling machine, lathe, etc., asdescribed in the aforesaid Unwin patent. Thus, as the part of themachine operating the switch moves back and forth, it turns the member2Ga through a small angle sufficient to throw the switch from oneposition to another and thereby effect a control operation, such as thereversal of the driving motor for the machine. Thus to move the shaft l0 counterclockwise, as viewed in Fig. 3, the operating member 20a, whichis journalled on the outer cylindrical end of the shaft ID and in turnmounted for rotation in the support I2, is turned in a counterclockwisedirection, as seen in Fig. 3, whereby the pin l6 engages and moves thelefthand end of the spring [4 toward the left, the other end of thespring bearing on the pin Hi. This end bearing on the pin applies acounterclockwise force to the armature member I! which tends to overcomethe force of the magnet. In any case, as the member 28 is turned, theprojection l3 engages the projection l9 and forcibly disengages thearmature member from the magnet whereupon the spring [4 snaps thearmature member counterclockwise to its opposite position.

It is believed that the reverse operation to the position shown in Fig.3 will be obvious from the preceding description.

As described and claimed in the aforesaid Unwin patent, I also provide ahelical over-center snap spring 29 whose function is to turn theoperating member a still farther in its operating direction after thearmature member has snapped to its other position. This additionalmovement of the operating member turns it out of the path of the part ofthe machine which operated it,

thus providin for free movement of the-machine.

Any suitable switching means can be secured to the shaft l0. As shown, Ihave provided four supports 30, 31, 32 and 33 mounted in two pairs .ateportion between said arms on opposite sides of the shaft. These supportsare made of a suitable electrically insulating material, such as amolded phenolic resin roduct. Each is provided with two stationarycontacts 34 and 35 mounted on electrically conducting U- shaped pieceswhose outer ends are provided with quickly detachable screw 36 for theconnection of electrical conductors thereto. Mounted on the shaft aretwo electrically insulating supports 31 and 38, each being provided witha pair of bridging contacts 39 and 40 mounted on opposite sides inposition to engage the corresponding pair of stationary contacts. Aterminal connection member 41, also made of an electrically insulatingmaterial, is mounted on a projection 42 on the support ll. These variousparts are secured to the supports II and [3 by suitable screws, as shownin the drawing.

As shown, the magnet 2| is supported on the upper pole piece 26 which inturn is secured to the upper end of a rectangular plate support 43. Thesupport 43 is in turn secured at its lower end by screws 44 and 45 tothe upper end of the support 12. A non-magnetic screw 46 secures themagnet 2| and lower pole piece 22 to the upper pole piece 26. Althoughthe screw 46 may be made of magnetic material and still make the deviceoperable, it is essential for best performance that this screw be ofnon-magnetic material. Otherwise it will tend to short-circuit theuseful working flux.

It will be understood that under certain conditions requiring the magnetto hold the armature in only one position, only one armature pole piece24 or 25 may be provided and only one magnet pole face 26a or 25b.

While I have shown a particular embodiment of my invention, it will beunderstood, of course, that I do not wish to be limited thereto sincemany modifications may be made, and I therefore contemplate by theappended claims to cover any such modifications as fallwithin the truespirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A switch comprising an operating shaft, a permanent bar magnetmounted in a fixed position with relation to said shaft and provided onone end with oppositely disposed pole faces, an armature member securedto said shaft having a pair of arms on opposite sides of said magnetprovided with pole pieces for engagement alternately with said magnetpole faces, a rotata, bly mounted operatingmember, a loose connectionbetween said operating member and said armature for disengaging saidarmature from said pole faces, a spring for snapping said armature toits other. position after such disengagement, said armature beingprovided with an arcuin closely spaced air gap relation with the otherend of said magnet, thereby to maintain a predetermined air gapirrespective of the final attracted position of said armature.

2. A switch comprising an operating shaft, a permanent bar magnetmounted in afixed position with relation to said shaft and provided onone end with oppositely disposedpole faces, an armature member securedto said shaft having a pair of arms on opposite sides of said magnetprovided with pole pieces for engagement alternately with said magnetpole faces, an operating member rotatably mounted on one end of saidshaft, a laterally extending projection on.said

operating member, a pair of pins extending lengthwise of said shaftmounted respectively on said armature and said projection, a helicalsnap spring surrounding'said operating member and having its endsextending laterally away from said shaft on opposite sides of said pins,said armature being provided with an arcuate portion between said armsin closely spaced air gap relation with the other end of said magnet,and projections on said armature spaced apart on opposite sides of saidfirst projection and engageable by said first projection upon turningmovement of said operating member thereby forcibly to move said armatureagainst the pull of one or the other of said oppositely disposed polefaces whereupon said armature is snapped by said spring into engagementwith the other of said magnet pole faces.

3. The combination in a snap action device, of a permanent magnetmounted in a fixed position and provided with a first pole face at oneend and a second pole face at its other end extending transversely withrespect to said first pole face, an armature pivotally mounted formoverange of movement of said armature, and means ment about an axissubstantially parallel with i said first pole face and provided with anarcuate i engagement with said second pole face and to an unattractedposition in spaced relation with said second pole face, said arcuateportion being coextensive with the angular movement of said armaturebetween said positions so that the surface of said arcuate portion is apredetermined distance from said first pole face throughout the foroperating said armature with a snap action into engagement with saidsecond pole face.

4. A switch comprising a permanent bar magnet mounted in a fixedposition and provided with oppositely disposed pole faces at one end, anarmature member mounted for limited rotation and having a pair of spacedapart arms on opposite sides of said magnet provided with pole piecesfor engagement alternately with said magnet pole faces when saidarmature is rotated between two positions, an operating member for saidarmature member, a snap spring between said operating member and saidarmature member for rotating said armature member with a snap actionbetween said two positions, said armature member being provided with anarcuate portion between said arms coextensive with the angular movementof said armature between said positions, and a third pole face on theother end of said bar magnet having its face in a predetermined spacedrelation with said arcuate portion throughout the entire movement ofsaid armature between said positions.

LOUIS T. RADER.

